1. Field
This invention relates to compound archery bows. It is particularly directed to an improved pulley assembly for such bows.
2. State of the Art
Compound archery bows commonly carry assemblies of pulley members (usually called “eccentrics” or “cams”) eccentrically mounted on axles in association with respective bow limbs. These limbs extend in opposite directions from a grip (usually comprising a central portion of a handle riser). The rigging for compound bows includes a bowstring trained around the pulley members of the system, the string being received by grooves or other functionally equivalent features at the perimeters of the pulleys. The eccentric pulley assemblies are conventionally mounted to rotate (pivot) on a stationary axle within a notch at the distal end of the limb, or within a bracket structure carried by the limb tip. The eccentrics include one or more pivot holes substantially offset from center, whereby to provide for a reduction in the holding force felt at the nocking point of the bowstring, as the string is moved to its fully drawn condition. The term “stationary axle” is intended to connote axles upon which pulley assemblies are free to pivot, in contrast to axles that themselves significantly and unavoidably rotate around a central axis (e.g. more than 180 degrees). In practice, it is normally immaterial to the operation of an archery bow whether an axle deemed stationary in this context actually rotates to some extent.
Compound bows and various exemplary riggings, including pulley assemblies, are described by U.S. Pat. Nos. 3,486,495; 3,990,425; 4,748,962; 4,774,927; 4,967,721 and 6,763,818, the disclosures of which are incorporated as a portion of this disclosure as general background concerning conventional constructions.
U.S. Pat. Nos. 3,990,425 and 6,990,870 propose rigging systems that cross-couple the pulley assembles of a compound bow so that they are constrained to move in unison, thereby providing a self-tuning function to the bow. The term “cross-couple” (sometimes “cross-coupling,” or “cross-coupled”) designates a rigging in which the cable end conventionally attached to the pulley axles are instead attached to a synchronizing sheave of the pulley assembly.
The '425 patent discloses pulley assemblies in which cross-coupling is accomplished through an anchoring arrangement that inherently imparts a leaning moment to the pulley assemblies. Specifically, the cables are all disposed to one side of the bowstring. The '870 patent disclosure includes riggings configured to apply cable forces more evenly, thereby reducing the twisting moment applied to the mounting axle of the assembly. Moreover, the '870 patent discloses cross-coupled pulley assemblies within the riggings of single-cam compound bows. In any case, the synchronizing pulley components incorporated into pulley assemblies to date have been integral; that is, they are fixed to the other components of the assembly and turn (pivot) in unison with the bowstring and cable pulley components
The conventional practice in constructing compound bows has been to mount all pulley components onto stationary axles. Originally, the pulleys were provided with bushings, rotatably mounted on an axle. More recently, these bushings have been replaced with bearing assemblies of various kinds, Exemplary bearing arrangements for compound bows are described and illustrated by U.S. Pat. No. 6,415,780, the disclosure of which is incorporated by reference for its description of such bearing arrangements and the advantages they offer. Commonly assigned, copending patent application Ser. No. 12/074,930 filed Mar. 7, 2007, discloses journal mounted axles integral with pulley assemblies. These arrangements accommodate increased spacing of bearing assemblies, further resisting the twisting moments applied to the assemblies during a shooting cycle.